The present invention relates generally to the detection and conversion of high frequency electromagnetic energy to electrical signals and, more particularly, to a scintillator array of fiber optic scintillators with optical gain for use with computed tomography systems.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward an object, such as a patient or a piece of luggage. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the object. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately results in the formation of an image.
Generally, the x-ray source and the detector array are rotated about the gantry within an imaging plane and around the object. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator.
Typically, each scintillator of a scintillator array converts x-rays to light energy. Each scintillator discharges light energy to a photodiode adjacent thereto. Each photodiode detects the light energy and generates a corresponding electrical signal. The outputs of the photodiodes are then transmitted to a data processing system.
Increasingly, there is a need for CT detector cells of reduced size. While reducing the relative size of each detector cell of a detector array has numerous advantages including increased CT system spatial resolution, reducing the size of each detector cell does result in some potentially detrimental effects. As the size of each cell is reduced, the light output/current output from each cell becomes increasingly small. In fact, the output signal from the cell can become so small that the signal is lost in the noise of the CT system""s data acquisition system. Furthermore, as a result of this reduced signal output with decreased scintillator size, the scintillator material choices that the detector can be fabricated from become quite limiting. This also negatively affects the optimization and selection of subsequent properties like primary speed, x-ray quantum detection efficient, afterglow, etc.
It would therefore be desirable to have a detector with built-in optical gain thereby providing improved detector signal output to a data processing system of a CT system.
The present invention is directed to a scintillator cell having optical gain overcoming the aforementioned drawbacks. The scintillator cell is comprised of material that yields a higher light output per absorbed x-ray photon thereby overcoming signal-to-noise limitations of data acquisition systems. As a result, the scintillator cell may also be comprised of a wider range of scintillator materials conducive to the optimization of other subsequent properties.
Therefore, in accordance with one aspect of the present invention, a fiber optic scintillator cell is provided. The fiber optic scintillator cell includes a first component formed of scintillating material and a second component formed of optically stimulated material.
In accordance with a further aspect of the present invention, a detector for a computed tomography system includes a fiber optic scintillator configured to receive high frequency electromagnetic energy having a first intensity and further configured to output light energy having a second intensity wherein the second intensity exceeds the first intensity. The detector further includes a photodiode optically coupled to the fiber optic scintillator and configured to detect the output from the fiber optic scintillator.
In accordance with yet a further aspect of the present invention, a computed tomography system is provided and includes a rotatable gantry having an opening to receive an object to be scanned. The system further includes a high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the object. A scintillator array having a plurality of scintillator cells is provided wherein each cell is configured to detect high frequency electromagnetic energy passing through the object. Each scintillator cell is further configured to output light having an intensity exceeding an intensity of the high frequency electromagnetic energy detected by the scintillator cell. The computed tomography system also includes a photodiode array optically coupled to the scintillator array and comprising a plurality of photodiodes. Each photodiode is configured to detect light output from a corresponding scintillator cell wherein each photodiode outputs a signal indicative of the light output of a corresponding scintillator cell. A data acquisition system (DAS) is connected to the photodiode array and configured to receive photodiode outputs. An image reconstructor is connected to the DAS and configured to reconstruct an image of the object from the photodiode outputs received by the DAS.
The present invention is also directed to a scintillator cell having improved light output characteristics. Therefore, in accordance with another aspect thereof, a method of manufacturing a fiber optic scintillator cell having optical gain is provided. A method includes the steps of fashioning a first component of scintillating material and fashioning a second component of optically stimulated material. The fiber optic scintillator cell may be manufactured by intermixing the first component and the second component in a single composite structure. The fiber optic scintillator cell may also be manufactured by forming the first component in a layer, forming the second component in a layer, and connecting the first component layer and the second component layer to one another in a single layered structure.
In accordance with yet another aspect of the present invention, a scintillator cell for use with a computed tomography imaging system is provided. The scintillator cell includes means for converting high frequency electromagnetic energy to light energy. The scintillator cell further includes means for amplifying the light energy output from the means for converting. The scintillator cell also includes means for outputting the amplified light energy to a light energy detector.
Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.